Headers for V8 cars, Please read
Lead Lap
Joined: Nov 2004
Posts: 441
Likes: 0
From: Alberta
Originally Posted by Lexy GS430
I have been reading this tread over, and over with little actions on these headers, please put me on the list if the headers can be made. $350 to $450 bucks no problem were can i send the money to. 
Lexus Champion
Joined: Feb 2001
Posts: 3,124
Likes: 32
From: Texas
NEWS....
I had 2 conversations with the craftsman today. In the first conversation, this morning, he told me that time was a problem and he was both short on labor force and long on projects. I told him I am would go ahead and build something and see if it can be duplicated. Not an easy task. I asked if he could send me the manifolds and jigs. He said OK...
Well... this evening he called me with the news that he has built a prototype driver side manifold. It is just tack welded at this point and doesn't have the catalyst flange or O2 sensor bung BUT it DOES fit inside the stock heatsheild!!! This is not needed and a surprise. There are some changes that we then discussed but he is shipping me the part tomorrow and I will post pictures as soon as I get it. I will then make some measurements, send it back and he will make the changes as well as start on the drivers side.
After ALL THIS TIME there is actually official PROGRESS
Stay tuned, things just got interesting. Expect the pictures within a week (UPS from AZ to TX is 2-3 days)
I had 2 conversations with the craftsman today. In the first conversation, this morning, he told me that time was a problem and he was both short on labor force and long on projects. I told him I am would go ahead and build something and see if it can be duplicated. Not an easy task. I asked if he could send me the manifolds and jigs. He said OK...
Well... this evening he called me with the news that he has built a prototype driver side manifold. It is just tack welded at this point and doesn't have the catalyst flange or O2 sensor bung BUT it DOES fit inside the stock heatsheild!!! This is not needed and a surprise. There are some changes that we then discussed but he is shipping me the part tomorrow and I will post pictures as soon as I get it. I will then make some measurements, send it back and he will make the changes as well as start on the drivers side.
After ALL THIS TIME there is actually official PROGRESS
Stay tuned, things just got interesting. Expect the pictures within a week (UPS from AZ to TX is 2-3 days)
Lexus Champion
Joined: Feb 2001
Posts: 3,124
Likes: 32
From: Texas
Since this project has actually produced some results it may be time for an update as over the past year a couple of things have changed from the original post.
First off, due to the choice for prototype building it looks like both drivers and passenger side manifolds will be built and sold as a set. Original quoted price was $400 un-coated mild steel or $600 ceramic coated mild steel. Some applications may want to modify the manifold so ordering uncoated may be better for them. Otherwise I would recommend the coated headers. The $200 premium is very reasonable as $100 per manifold is very fair.
Design, the prototype passenger side manifold fits inside the stock heat shield. The drivers side may not. Pre 1998 and post 2000 shields are different and definitely will not fit either side. Due to this the design of the manifolds is dictated by the available space and location of the catalysts. They will NOT look like the pictures at the beginning of this thread. The idea is to build a manifold that retains as much of the exhaust energy as possible and directs it downstream within the confines of the available space. This is something the stock manifolds do not do well so this should dramatically improve exhaust flow and should yeild the target 20rwhp gain when used with good flowing parts after the catalysts. Please do NOT consider this power target as a guarantee. Final results could be higher or lower and will vary from vehicle to vehicle.
Primary vehicle fitment is for the 1998-2000 GS400. For these cars these headers should fit in the stock location and work with the stock catalysts. Final fitment of heatsheilds should not be expected but may be possible at least on the passenger side. This means the stock Y pipe and the rest of the stock exhaust could be used although not recommended for best performance.
Alternate bolt in fitment should apply to the 1998-2000 LS400 and 1998-2000 SC400. The above statements about the GS400 should also apply.
Possible direct bolt on (except for EGR, see below paragraphs) may apply to the 1995-1997 LS400 and possibly the 1996-1997 SC400. I learned this after I gained access to some factory documents that indicate the twin tube style manifold actually originally came on the 1995 260hp/270tq LS400. Catalyst outlet flange, O2 sensor location and total dimensions are not confirmed. EGR would need to be added. This same rating applied to the 1996 SC400 but I do not have access to drawings for this year SC400 manifolds. The 1995 SC400 had the previous 250hp/260tq rated engine and those had the single tube manifold.
Installation with modifications should work on the 1990-1994 LS400 and the 1992-1995 SC400. At the very least installation will require moving the stock catalysts and using a different Y pipe. No EGR provisions will be made so the installer will need to consider this if they choose to retain EGR. 1996-1997 SC400s may or may not have this same requirement.
2001+ GS430s, LS430s and SC430s are unknown. What is known is that Lexus went back to a single tube manifold to heat the catalysts faster. This style is presumed to be more restrictive than the dual tube design and is a good reason that power ratings did not go up with the larger engine vs the 400s. The 430s also run 3 catalysts; 2 bolt to the manifolds and one is welded to the stock Y pipe after the Y intersection. Catalysts flange size, bolt pattern and angle are unknown and therefore 430 owners should expect to definitely fabricate new exhaust after the first 2 cats and possibly need a transition from the headers to the cat inlets.
That is all for now but I will post more as this project proceeds.
Stay tuned.
First off, due to the choice for prototype building it looks like both drivers and passenger side manifolds will be built and sold as a set. Original quoted price was $400 un-coated mild steel or $600 ceramic coated mild steel. Some applications may want to modify the manifold so ordering uncoated may be better for them. Otherwise I would recommend the coated headers. The $200 premium is very reasonable as $100 per manifold is very fair.
Design, the prototype passenger side manifold fits inside the stock heat shield. The drivers side may not. Pre 1998 and post 2000 shields are different and definitely will not fit either side. Due to this the design of the manifolds is dictated by the available space and location of the catalysts. They will NOT look like the pictures at the beginning of this thread. The idea is to build a manifold that retains as much of the exhaust energy as possible and directs it downstream within the confines of the available space. This is something the stock manifolds do not do well so this should dramatically improve exhaust flow and should yeild the target 20rwhp gain when used with good flowing parts after the catalysts. Please do NOT consider this power target as a guarantee. Final results could be higher or lower and will vary from vehicle to vehicle.
Primary vehicle fitment is for the 1998-2000 GS400. For these cars these headers should fit in the stock location and work with the stock catalysts. Final fitment of heatsheilds should not be expected but may be possible at least on the passenger side. This means the stock Y pipe and the rest of the stock exhaust could be used although not recommended for best performance.
Alternate bolt in fitment should apply to the 1998-2000 LS400 and 1998-2000 SC400. The above statements about the GS400 should also apply.
Possible direct bolt on (except for EGR, see below paragraphs) may apply to the 1995-1997 LS400 and possibly the 1996-1997 SC400. I learned this after I gained access to some factory documents that indicate the twin tube style manifold actually originally came on the 1995 260hp/270tq LS400. Catalyst outlet flange, O2 sensor location and total dimensions are not confirmed. EGR would need to be added. This same rating applied to the 1996 SC400 but I do not have access to drawings for this year SC400 manifolds. The 1995 SC400 had the previous 250hp/260tq rated engine and those had the single tube manifold.
Installation with modifications should work on the 1990-1994 LS400 and the 1992-1995 SC400. At the very least installation will require moving the stock catalysts and using a different Y pipe. No EGR provisions will be made so the installer will need to consider this if they choose to retain EGR. 1996-1997 SC400s may or may not have this same requirement.
2001+ GS430s, LS430s and SC430s are unknown. What is known is that Lexus went back to a single tube manifold to heat the catalysts faster. This style is presumed to be more restrictive than the dual tube design and is a good reason that power ratings did not go up with the larger engine vs the 400s. The 430s also run 3 catalysts; 2 bolt to the manifolds and one is welded to the stock Y pipe after the Y intersection. Catalysts flange size, bolt pattern and angle are unknown and therefore 430 owners should expect to definitely fabricate new exhaust after the first 2 cats and possibly need a transition from the headers to the cat inlets.
That is all for now but I will post more as this project proceeds.
Stay tuned.
Lexus Champion
Joined: Feb 2001
Posts: 3,124
Likes: 32
From: Texas
Mild steel. With ceramic coating the mild steel should last indefinitely and have good properties. Stainless would raise the price hundreds.
Thickness is .065
I should have the prototype passenger header within days. I will post pics then.
Thickness is .065
I should have the prototype passenger header within days. I will post pics then.
Last edited by JBrady; Mar 14, 2005 at 07:11 PM.
